Process for the production of sticky polymers

ABSTRACT

A process for the production of EPM or EPDM comprising contacting ethylene, propylene, and, optionally, one or more dienes, in a fluidized bed, at a temperature at or above the sticking temperature of the product resin, under polymerization conditions, with 
     (i) a prepolymer containing a transition metal catalyst precursor with the proviso that the prepolymer is not sticky at the process temperature; 
     (ii) a hydrocarbyl aluminum and/or a hydrocarbyl aluminum halide cocatalyst,; and, optionally, 
     (iii) a halocarbon promoter; and, optionally, 
     (iv) an inert particulate material having a mean particle size in the range of about 0.01 to about 150 microns wherein the particulate material is either contained in the prepolymer or is independent of the prepolymer, 
     wherein the amount of prepolymer or the combined amount of prepolymer and inert particulate material is sufficient to essentially prevent agglomeration of the fluidized bed and the product resin.

This application is a Continuation of prior U.S. application Ser. No.08/029,821 Filing Date Mar. 11, 1993, now U.S. Pat. No. 5,376,743.

TECHNICAL FIELD

This invention relates to the production of sticky polymers,particularly elastomers having a crystallinity of less than about 10percent by weight.

BACKGROUND INFORMATION

The production of amorphous EPR elastomers in a gas phase fluidized bedprocess above their sticking temperatures is difficult due toagglomeration of the sticky, granular resin bed particles underpolymerization conditions.

The term "sticky polymer" is defined as a polymer which, althoughparticulate at temperatures below the sticking temperature, agglomeratesat temperatures at or above the sticking temperature. The term "stickingtemperature", which, in the context of this specification, concerns thesticking temperature of particles of polymer in a fluidized bed, isdefined as the temperature at which fluidization ceases due to theagglomeration of particles in the bed. The agglomeration may bespontaneous or occur on short periods of settling.

A polymer may be inherently sticky due to its chemical or mechanicalproperties or pass through a sticky phase during the production cycle.Sticky polymers are also referred to as non-free flowing polymersbecause of their tendency to compact into aggregates of much larger sizethan the original particles and not flow out of the relatively smallopenings in the bottom of product discharge tanks or purge bins.Polymers of this type show acceptable fluidity in a gas phase fluidizedbed reactor; however, once motion ceases, the additional mechanicalforce provided by the fluidizing gas passing through the distributorplate is insufficient to break up the aggregates which form and the bedwill not refluidize. These polymers are classified as those, which havea minimum bin opening for free flow at zero storage time of up to twofeet and a minimum bin opening for free flow at storage times of greaterthan five minutes of 4 to 8 feet or more.

Because of the tendency to agglomerate, sticky polymers are difficult toproduce in typical gas phase processes, which are usually carried out influidized beds. Both economic and safety/environmental considerationsindicate, however, that fluidized bed type polymerization is preferredfor the manufacture of polymers that can exist in a granular,fluidizable form.

Although polymers that are sticky can be produced in non-gas phaseprocesses, there are certain difficulties associated with the productionof such products in, for example, slurry or bulk monomer polymerizationprocesses. In such processes, the diluent or solvent is present in theresins exiting the reaction system at a high concentration leading tosevere resin purging problems, particularly if the material in questionis a low molecular weight resin or a very low crystallinity resin.Environmental considerations are such that the dissolved monomers anddiluent must be removed from the polymer prior to its exposure to air.Safety also dictates the removal of residual hydrocarbons so that closedcontainers containing the polymers will not exceed safe volatiles levelsin the gas head space over the resin. The safety and environmentalconcerns are accompanied by a definite economic factor in determining apreference for a gas phase fluid bed reaction system. The low number ofmoving parts and the relative lack of complexity in a basic fluidizedbed process enhances the operability of the process and typicallyresults in lower costs of production. Low costs of production are due,in part, to low volumes of recycled process streams and a high unitthroughput.

Three major process types have been used for the production of some orall of these sticky resins, i.e., the bulk monomer slurry process; thediluent slurry process; and the solution process. All of theseprocesses, although suitable for the production of many different typesof polymers have deficiencies that are not present in the fluidized bedreaction system. The absence of large volumes of solvent or liquidmonomer increases the safety of the system. The granular nature of theresultant polymer increases the flexibility of the system in that bothgranular resin and compounded resin can be delivered to the customer.The granular, porous nature of the polymer also facilitates purging ofunwanted monomer to environmentally safe levels. A wide range ofmolecular weights can be produced in a fluidized bed, i.e., fromultrahigh molecular weights having a melt index of less than 0.001 gramper 10 minutes to relatively low molecular weights having a melt indexof up to 100 grams per 10 minutes. Melt index is measured under ASTMDo1238, Condition E, at 190° C., and reported as grams per 10 minutes.The high heat removal capacity of a fluidized bed (due to thecirculation of the fluidizing gas) and the ability to control reactionconcentrations without the limitations imposed by the solubility ofcomponents such as hydrogen in the diluent are also desirable featuresof the fluidized bed process.

It is clear, then, that the production of polymer by means of afluidized bed reaction system is advantageous. A typical system of thistype is described in U.S. Pat. No. 4,482,687. Unfortunately, this systemrequires that the granular product be free-flowing. Industry hasgenerally dealt with the problem of sticky polymers by avoidingoperating regimes at or above the sticking temperature of the polymer.Low pressure polymerization of olefins in a gas phase reactor usingtransition metal catalysts is generally performed at temperatures below120° C.. Where high levels of comonomers are used in combination withethylene and crystallinity levels are reduced below 30 percent byweight, the sticking temperature of the olefin polymer can be close tothe polymerization temperature. Under such conditions, in either afluidized bed or a stirred gas/solid phase reactor, stickiness of theresin particles becomes a problem. The stickiness problem becomes evenmore critical with copolymers of ethylene and propylene (EPMs) andethylene/propylene/diene/terpolymers (EPDMs) having a crystallinecontent of less than about 10 percent by weight. These particularpolymers are also known as EPRs, i.e., ethylene/propylene copolymerrubbers. Commercially desirable EPMs and EPDMs contain about 20 to about55 percent by weight propylene and the EPDMs contain about 2 to about 15percent by weight ethylidene norbornene (ENB).

EPRs are practically amorphous with glass transition temperatures ofminus 50° C. to minus 60° C. At temperatures above the glass transitiontemperature, EPM and EPDM are rubbers whose viscosity decreases, likeall rubbers, exponentially with increases in temperature. This viscositydecrease with rising temperatures is a major obstacle in the fluidizedbed production of EPR because agglomeration increases as particlesurface viscosity decreases.

At temperatures above about 30° C., amorphous EPM particles become sosticky that fluidized bed polymerization cannot be carried out reliably.EPDM particles are even stickier than EPM due to the presence of solubleliquid dienes such as ethylidene norbornene.

The stickiness problem can be reduced in a fluidized bed by theintroduction of a fluidization aid, and this is described in U.S. Pat.No. 4,994,534. While this procedure is generally effective, it isdeficient in the preparation of amorphous or nearly amorphous resins attemperatures at or above their sticking temperatures, i.e., underconditions of maximum stickiness. In this ease, large quantities of thefluidization aid, about 15 to about 50 percent by weight based on theweight of the final product, are required. This, in turn, increases thecost of material; requires large quantities of fluidization aid to betreated to ensure inertness; reduces the polymer throughput of thereactor; increases residues; limits the end use applications of theresin; can affect polymer properties in an undesirable way, e.g., byincreasing block or gel formation; and imposes various other economicpenalties.

The problem lies, then, in how to produce essentially amorphous ornearly amorphous EPRs at temperatures at or higher than their stickingtemperatures, since the higher the temperature the greater theproductivity, while at the same time reducing the amount of fluidizationaid and, thus, fluidization aid residues, or eliminating thefluidization aid altogether.

DISCLOSURE OF THE INVENTION

An object of this invention is to produce an amorphous or a nearlyamorphous EPR in a fluidized bed at or above the sticking temperature ofthe EPR using a minimal amount of, or no, fluidization aid.

Other objects and advantages will become apparent hereafter.

According to the present invention, the above object is met by a processfor the production of EPM or EPDM comprising contacting ethylene,propylene, and, optionally, one or more dienes, in a fluidized bed, at atemperature at or above the sticking temperature of the product resin,under polymerization conditions, with

(i) prepolymer containing a transition metal catalyst with the provisothat the prepolymer is not sticky at the process temperature;

(ii) a hydrocarbyl aluminum and/or a hydrocarbyl aluminum halidecocatalyst; and, optionally,

(iii) a halogen containing promoter; and, optionally,

(iv) an inert particulate material having a mean particle size in therange of about 0.01 to about 150 microns wherein the particulatematerial is either contained in the prepolymer or is independent of theprepolymer,

wherein the amount of prepolymer or the combined amount of prepolymerand inert particulate material are sufficient to essentially preventagglomeration of the fluidized bed and the product resin.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The prepolymer used in the process of the invention is one whichcontains a transition metal catalyst, which is suitable for producingEPM and EPDM. This will include the Ziegler-Natta catalysts. Thesecatalysts are exemplified by the vanadium, titanium, and chromium basedcatalysts described in U.S. Pat. Nos. 4,508,842; 4,302,565; 4,414,132;and 4,101,445, and can include spray dried catalysts. A technique forthe prepolymerization of these types of catalysts can be found in U.S.Pat. No. 4,970,279. As noted above, the inert particulate material canbe incorporated into the prepolymer or introduced into the fluidized bedreactor independently. Typically, the prepolymerization is carried outin the liquid phase in a similar manner to a diluent slurrypolymerization. The catalyst system used in the prepolymerization isgenerally the same one that will be used in the fluidized bedpolymerization. The difference lies in the monomers used and weightratio of monomer(s) to catalyst precursor, which is at least about 10:1,and is typically about 50:1 to about 300:1. It should be pointed outthat the numbers vary with the particular catalyst selected. Themonomers and process conditions must be such that the prepolymer productper se is not sticky at the polymerization process temperatures, whichare at or above the sticking temperature of the EPM or EPDM product.Examples of the prepolymers are homoprepolymers of ethylene,ethylene/propylene coprepolymers, ethylene/1-hexene coprepolymers,ethylene/propylene/1-hexene terprepolymers, and ethylene/propylene/dieneterprepolymers, provided that they are of sufficiently highcrystallinity or viscosity to be non-sticky.

The amount of prepolymer formed, in terms of grams of prepolymer pergram of catalyst precursor, generally depends on the composition of theprepolymer, the composition of the polymer being produced, and theproductivity of the catalyst employed. The prepolymer loading is chosenso as to minimize the prepolymer residue in the product resin whilestill providing agglomeration protection. Stickier products generallyrequire either higher initial loadings or higher residues in the productor both to provide equivalent agglomeration protection. More productivecatalyst systems generally require higher initial loadings, but resultin lower product residues at equivalent agglomeration protection. Whenusing ethylene homoprepolymers or ethylene/propylene coprepolymers with,for example, a vanadium catalyst system, including a supported vanadiumtrihalide/electron donor reaction product as precursor with a modifier,a halocarbon promoter, and a hydrocarbyl aluminum cocatalyst, prepolymerloading can be in the range of about 10 to about 500 grams of prepolymerper gram of catalyst precursor and is preferably in the range of about50 to about 300 grams of prepolymer per gram of catalyst precursor.

As noted above, the prepolymer is not sticky at the temperature at whichthe process is carried out. When used by itself, i.e., without thefluidization aid, the amount of prepolymer is sufficient to essentiallyprevent agglomeration of the fluidized bed, which is made up of resinparticles, and the product resin. Preferably, the amount of prepolymerused in this case is limited to the amount which will provide about 3 toabout 20 percent by weight of prepolymer in the product resin based onthe weight of the product resin and is most preferably kept in the rangeof about 3 to about 15 percent by weight. When the prepolymer is usedtogether with the fluidization aid, the combined amount of prepolymerand inert particulate material (the fluidization aid) is sufficient toessentially prevent agglomeration of the fluidized bed, which is made upof resin particles, and the product resin. Preferably, the amount ofprepolymer used in this embodiment of the process is limited to theamount which will provide about 1 to about 12 percent by weight ofprepolymer in the product resin based on the weight of the product resinand is most preferably kept in the range of about 2 to about 8 percentby weight.

A typical vanadium based catalyst system useful in the preparation ofthe prepolymer and the EPM or EPDM product is comprised of (a) avanadium compound or the reaction production of a vanadium compound andan electron donor as catalyst precursor; (b) a hydrocarbyl aluminumand/or a hydrocarbyl aluminum halide cocatalyst; and, optionally, (c) ahalocarbon promoter. This system can be described in more detail asfollows.

The vanadium compound can be any of the group of vanadium compounds wellknown to be useful as or in catalyst precursors in olefin polymerizationprocesses. Examples are vanadium acetylacetonates, vanadium trihalides,vanadium tetrahalides, and vanadium oxyhalides. The halides aregenerally chlorides, bromides, or iodides, or mixtures thereof. Morespecific examples of these compounds are VCl₃, VCl₄, vanadium(acetylacetonate )₃, vanadyl triacetylacetonate, VO(OC₂ H₅ )Cl₂,VOCl(OC₂ H₅)₂, VO(OC₂ H₅)₃, and VO(OC₄ H₉)₃.

The electron donor, if used in the catalyst precursor, is an organicLewis base, liquid at temperatures in the range of about 0° C. to about200° C., in which the vanadium compounds are soluble.

The electron donor can be an alkyl ester of an aliphatic or aromaticcarboxylic acid, an aliphatic ketone, an aliphatic amine, an aliphaticalcohol, an alkyl or cycloalkyl ether, or mixtures thereof, eachelectron donor having 2 to 20 carbon atoms. Among these electron donors,the preferred are alkyl and cycloalkyl ethers having 2 to 20 carbonatoms; dialkyl, diaryl, and alkylaryl ketones having 3 to 20 carbonatoms; and alkyl, alkoxy, and alkylalkoxy esters of alkyl and arylcarboxylic acids having 2 to 20 carbon atoms. The most preferredelectron donor is tetrahydrofuran. Other examples of suitable electrondonors are methyl formate, ethyl acetate, butyl acetate, ethyl ether,dioxane, di-n-propyl ether, dibutyl ether, ethyl formate, methylacetate, ethyl anisate, ethylene carbonate, tetrahydropyran, and ethylpropionate.

While an excess of electron donor is used initially to provide thereaction product of vanadium compound and electron donor, the reactionproduct finally contains about 1 to about 20 moles of electron donor permole of vanadium compound and preferably about 1 to about 10 moles ofelectron donor per mole of vanadium compound.

A modifier, if used, can have the formula BX₃ or AlR.sub.(3-a) X_(a)wherein each R is an alkyl radical having 1 to 14 carbon atoms and isthe same or different; each X is chlorine, bromine, or iodine and is thesame or different; and a is 0, 1 or 2. While one or more modifiers canbe used, two different modifiers are preferred. Preferred modifiersinclude alkylaluminum mono- and dichlorides wherein each alkyl radicalhas I to 6 carbon atoms, boron trichloride, and the trialkylaluminums. Aparticularly preferred modifier is diethylaluminum chloride. About 0.1to about 10 moles, and preferably about 0.2 to about 2.5 moles, ofmodifier are used per mole of electron donor. The molar ratio ofmodifier to vanadium is in the range of about 1:1 to about 10:1 and ispreferably in the range of about 2:1 to about 5:1.

Promoters are an optional component of the catalyst system. Chlorinatedor perchlorinated esters are suitable promoters. Examples of theseesters are Cl₃ CCOOC₂ H₅ ; CCl₃ CCl═CClCOOC₄ H₉ ; C₆ H₅ CCl₂ COORwherein R is an alkyl radical having 1 to 8 carbon atoms: and Cl₂C═CCl--CCl₂ COOC₄ H₉. Other suitable halocarbon promoters have thefollowing formula:

    R.sub.y CX.sub.(4-y)

wherein

R=hydrogen or an unsubstituted or halogen substituted alkyl radicalhaving 1 to 6 carbon atoms;

X=a halogen; and

y=0, 1, or 2.

Preferred promoters of this group include flouro-, chloro-, andbromo-substituted methane and ethane wherein there are at least two Xatoms, e.g., methylene dichloride, 1,1,1-trichloroethane, chloroform,CBr₄, CFCl₃, hexachloroethane, CH₃ CCl₃, and CF₂ ClCCl₃. The first threementioned promoters are especially preferred. About 0.1 to about 10moles, and preferably about 0.2 to about 2 moles, of promoter can beused per mole of cocatalyst.

The hydrocarbyl aluminum cocatalyst can be represented by the formula R₃Al or R₂ AlX wherein each R is independently alkyl, cycloalkyl, aryl, orhydrogen; at least one R is hydrocarbyl; and two or three R radicals canbe joined to form a heterocyclic structure. Each R, which is ahydrocarbyl radical, can have 1 to 20 carbon atoms, and preferably has 1to 10 carbon atoms. X is a halogen, preferably chlorine, bromine, oriodine.

Examples of hydrocarbyl aluminum compounds are as follows:triisobutylaluminum, trihexylaluminum, diisobutylaluminum hydride,dihexylaluminum dihydride, diisobutylhexylaluminum, isobutyldihexylaluminum, trimethylaluminum, triethylaluminum, tripropylaluminum,triisopropylaluminum, tri-n-butylaluminum, trioctylaluminum,tridecylaluminum, tridodecylaluminum, tribenzylaluminum,triphenylaluminum, trinaphthylaluminum, tritolylaluminum,dibutylaluminum chloride, diethylaluminum chloride, and ethylaluminumsesquichloride. The cocatalyst compounds can also serve as modifiers.

Where it is desired to support the precursor, silica is the preferredsupport. Other suitable supports are inorganic oxides such as aluminumphosphate, alumina, silica/alumina mixtures, silica modified with anorganoaluminum compound such as triethylaluminum, and silica modifiedwith diethylzinc. A typical support is a solid, particulate, porousmaterial essentially inert to the polymerization. It is used as a drypowder having an average particle size of about 10 to about 250 micronsand preferably about 30 to about 100 microns; a surface area of at least200 square meters per gram and preferably at least about 250 squaremeters per gram; and a pore size of at least about 100 angstroms andpreferably at least about 200 angstroms. Generally, the amount ofsupport used is that which will provide about 0.1 to about 1.0 millimoleof vanadium per gram of support and preferably about 0.4 to about 0.9millimole of vanadium per gram of support. Impregnation of the abovementioned catalyst precursor into a silica support is accomplished bymixing the precursor and silica gel in the electron donor solvent orother solvent followed by solvent removal under reduced pressure.

Where modifiers are used, they are usually dissolved in an organicsolvent such as isopentane and impregnated into the support followingimpregnation of the vanadium compound or complex, after which thesupported catalyst precursor is dried. The cocatalyst is preferablyadded separately neat or as a solution in an inert solvent, such asisopentane, to the prepolymerization or polymerization reaction at thesame time as the flow of ethylene is initiated.

Useful molar ratios for a vanadium based catalyst system are about asfollows:

    ______________________________________                    Broad   Preferred    ______________________________________    ED:V (where ED is used)                      1:1 to 20:1                                1:1 to 10:1    modifier:V        1:1 to 10:1                                2:1 to 5:1    ______________________________________

The fluidization aid is an inert particulate material having a meanparticle size in the range of about 0.01 to about 150 microns,preferably to about 10 microns. As noted above, the combined amount ofprepolymer and fluidization aid is sufficient to essentially preventagglomeration of the fluidized bed and the product resin. Preferably,the amount of fluidization aid used can be in the range of about 1 toabout 15 percent by weight, based on the weight of the final EPRproduct, and is most preferably in the range of about 1 to about 10percent by weight. The mean particle size can refer to the particle perse or an aggregate as in the case of carbon black or silica.

The particulate materials employed in subject process are materialswhich are chemically inert to the reaction except in some cases wherethe fluidization aid reacts with the cocatalyst. Examples of particulatematerials include carbon black, silica, clays, and other like materials.Carbon black and silica are the preferred materials. The carbon blackmaterials employed can have a primary particle size of about 10 to about100 nanometers and an average size of aggregate (primary structure) ofabout 0.1 to about 10 microns. The specific surface area of the carbonblack is about 30 to about 1,500 square meters per gram and display adibutylphthalate (DBP) absorption of about 80 to about 350 cubiccentimeters per 100 grams.

With respect to the fluidized bed reactor, the fluidization aids arepreferably inserted high in the fluidized bed, at the top or just aboutthe top of the bed, to prevent the resin from sticking to the walls ofthe reactor (sheeting).

The silicas which can be employed are amorphous silicas having a primaryparticle size of about 5 to about 500 nanometers and an average size ofaggregate of about 0.1 to about 120 microns. They have a specificsurface area of about 50 to about 500 square meters per gram and adibutylphthalate (DBP) absorption of about 100 to about 400 cubiccentimeters per 100 grams.

The clays which can be employed according to the present invention havean average particle size of about 0.01 to about 10 microns and aspecific surface area of about 3 to about 30 square meters per gram.They exhibit oil absorption of about 20 to about 100 cubic centimetersper 100 cubic centimeters.

The amount of particulate material utilized generally depends on thetype of particulate and the type of polymer produced. When utilizingcarbon black or silica as the particulate material, they are preferablyemployed in amounts of about 1 to about 10 percent by weight, and, mostpreferably, about 2 to about 8 percent by weight, based on the weight ofthe final product produced. When clays are employed as the particulatematerial, the amount preferably ranges from about 5 to about 15 percentby weight based on the weight of the final product.

It is preferred to treat the particulate material prior to entry intothe reactor to remove traces of moisture and oxygen. This can beaccomplished by purging the material with nitrogen gas, and heating,using conventional procedures.

A typical prepolymerization can be carried out in a slurryprepolymerizer. The equipment includes a monomer feed system, a reactionvessel, and an inert screener. The reactor is a jacketed pressure vesselwith a helical ribbon agitator to give good solids mixing, and with abottom cone to facilitate solids discharge. Ethylene is fed fromcylinders, with the pressure regulated, through 4A or 13X molecularsieves to remove impurities, and then through a flow meter to measureflow rate. Other olefins, if required, are fed from cylinders via a diptube with nitrogen pressure supplied to the cylinder headspace. Theyalso pass through 4A or 13X molecular sieves and through a flow meter.The monomers can be fed to either the reactor headspace or subsurface,with subsurface preferred as it increases the reaction rate byeliminating one mass transfer step. Temperature is controlled with aclosed loop tempered water system. Pressure is controlled with avent/make-up system.

The finished prepolymerized catalyst is screened to remove skins,agglomerates, and other types of oversize particles that could causefeeding difficulties into the gas phase reactor. The screening is donewith a vibratory screener with a 20 mesh screen. The screener is keptunder a nitrogen atmosphere to maintain the prepolymerized catalystactivity. Oversize material is collected for disposition. The desiredundersize fraction is discharged into a cylinder for storage andshipping.

The typical prepolymerization is a slurry polymerization of ethyleneand, optionally, a comonomer under mild conditions. Isopentane, hexane,and heptane can be used as the solvent, with isopentane preferred forits higher volatility. Mild conditions are necessary to minimizecatalyst decay during the prepolymerization so that there is sufficientactivity for the subsequent gas phase polymerization, which may occurmonths after the prepolymerization. Such conditions will vary withdifferent catalyst systems, but are typically temperatures of about 25to about 70° C., monomer partial pressures of about 15 to about 40 psi,and levels of cocatalyst and catalyst promoter of about 1 to about 5moles per mole of vanadium. The prepolymer loading ranges from about 10to about 500 grams per gram of supported catalyst precursor, preferablyfrom about 50 to about 300 grams per gram. The comonomer content of theprepolymer ranges from 0 to 15 weight percent. Hydrogen, or other chaintransfer agents, can be added at the start of polymerization orthroughout the polymerization to control molecular weight. Additionalolefins or dienes may also be added. When the polymerization iscomplete, the agitator is stopped and the solids are allowed to settleso that the excess solvent can be removed by decanting. The remainingsolvent is removed by drying, using low temperatures to avoid catalystdecay. The dried prepolymer catalyst is discharged to a storage cylinderthrough an inert screener, to remove oversize (+20 mesh) material.

While the preferred catalyst system is a vanadium based catalyst system,titanium based catalyst systems can also be useful in the preparation ofEPM and EPDM.

A typical titanium based catalyst system comprises:

(a) a catalyst precursor having the formula Mg_(a) Ti(OR)_(b) X_(c) (ED)_(d) wherein

R is an aliphatic or aromatic hydrocarbon radical having 1 to 14 carbonatoms or COR' wherein R' is a aliphatic or aromatic hydrocarbon radicalhaving 1 to 14 carbon atoms;

each OR group is the same or different;

X is independently chlorine, bromine or iodine;

ED is an electron donor;

a is 0.5 to 56;

b is 0, 1, or 2;

c is 2 to 116; and

d is 2 to 85

(b) at least one modifier having the formula BX₃ or AlR.sub.(3-b) X_(b)wherein each R is alkyl or aryl and is the same or different, and X andb are as defined above for component (a).

wherein components (a) and (b) are impregnated into an inorganicsupport; and

(c) a hydrocarbyl aluminum cocatalyst.

This titanium based catalyst system and its method for preparation aredisclosed in U.S. Pat. No. 4,302,565. The precursor is prepared from atitanium compound, a magnesium compound, and an electron donor.

Titanium compounds, which are useful in preparing these precursors, havethe formula Ti(OR)_(b) X_(e) wherein R, X, and b are as defined abovefor component (a); e is an integer from 1 to 4; and b+e is 3 or 4.Examples of titanium compounds are TICl₃, TICl₄, Ti(OC₂ H₅)₂ Br₂, Ti(OC₆H₅)Cl₃, Ti(OCOCH₃)Cl₃, and Ti(OCOC₆ H₅)Cl₃.

The magnesium compounds, which are useful in preparing these precursors,include magnesium halides such as MgCl₂, MgBr₂, and MgI₂. AnhydrousMgCl₂ is a preferred compound. About 0.5 to 56, and preferably about 1to 10, moles of the magnesium compounds are used per mole of titaniumcompounds.

The electron donor, the modifier, the support, and the hydrocarbylaluminum cocatalyst are the same as those used in the vanadium basedcatalyst system described above.

The modifiers are usually dissolved in an inorganic solvent such asisopentane and impregnated into the support following impregnation ofthe titanium based complex, after which the catalyst precursor is dried.The cocatalyst is preferably added separately neat or as a solution inan inert solvent, such as isopentane, to the prepolymerization or thepolymerization reaction at the same time as the flow of the ethylene isinitiated.

The polymerization is conducted in the gas phase, preferably in afluidized bed made up of particulate EPM or EPDM. The fluidized bed canbe a stirred fluidized bed reactor or a fluidized bed reactor, which isnot stirred. In terms of the fluidized bed, a superficial velocity ofabout 1 to about 4.5 feet per second and preferably about 1.5 to about3.5 feet per second can be used. The total reactor pressure can be inthe range of about 150 to about 600 psia and is preferably in the rangeof about 250 to about 500 psia. The ethylene partial pressure can be inthe range of about 25 psi to about 350 psi and is preferably in therange of about 80 psi to about 250 psi. The gaseous feed streams ofethylene, propylene, and hydrogen are preferably fed to the reactorrecycle line while liquid ethylidene norbornene or another diene, ifused, and the cocatalyst solution are preferably fed directly to thefluidized bed reactor to enhance mixing and dispersion. Feeding liquidstreams into the reactor recycle line can cause a rapid buildup of afouling layer resulting in very poor reactor operation. The prepolymercontaining the catalyst precursor and, optionally, the fluidization aidis transferred into the fluidized bed from the catalyst feeder. Wherethe fluidization aid is used and is independent of the prepolymer, it isintroduced into the fluidized bed in the manner mentioned above. Thecomposition of the EPM or EPDM product can be varied by changing thepropylene/ethylene molar ratio in the gas phase and the dieneconcentration in the fluidized bed. The product is intermittentlydischarged from the reactor as the bed level builds up withpolymerization. The production rate is controlled by adjusting thecatalyst feed rate.

In some instances when feeding a prepolymerized catalyst where nofluidization aid is used, adjusting the catalyst feed rate to controlthe production rate can result in too little prepolymer residue toprovide agglomeration protection. In these cases, it is found to beadvantageous to adjust the production rate by introducing small amountsof a reversible catalyst poison while maintaining a higher prepolymerfeed rate. In addition to increasing the prepolymer residue in theproduct resin, it is found that the reversible poison moderatesprepolymer activity, poisons any catalyst sites on the prepolymersurface that could produce sticky resin, permits operation at higherC_(3/) C₂ molar ratios, and enhances tolerance to process upsets, all ofwhich contribute to avoiding defluidization due to stickiness. Forexample, if the final product is an ethylene-propylene copolymer,introduction of about 0.5 to about 1.0 percent by weight based on thefluidized bed weight of ethylidene norbornene controls the prepolymerresidue at the desired level for preventing agglomeration of about 3 toabout 15 percent by weight.

The molar ratio of monomers in the reactor will be different fordifferent catalyst systems, as is well-known to those skilled in theart. The propylene/ethylene molar ratio is adjusted to control the levelof propylene incorporated into the terpolymer. For the vanadium catalystdescribed above, a range of about 0.35:1 to about 3:1 is preferred. Thehydrogen/ethylene molar ratio is adjusted to control average molecularweights of the terpolymer. For the same catalyst system, a range ofabout 0.001:1 to about 0.2:1 is preferred. The level of diene in thebed, if used, is in the range of about 1 to about 15 weight percentbased on the weight of the bed, and is preferably in the range of about2 to about 10 weight percent. Examples of useful dienes, in addition toethylidene norbornene (ENB), are 1,4-hexadiene and dicyclopentadienedimer.

Additional steps can be taken to reduce agglomeration arising fromcauses other than softening temperature.

The product discharge line between the reactor and the product pot isoften plugged up with chunks between intervals of product drops. Acontinuous purge flow of nitrogen in the line prevents the pluggingproblem. Also, coating the reactor surface with a low surface energymaterial is shown to be beneficial to slow down the rate of foulingbuild up. In addition, control of the electrostatic level in the bedprevents static induced particle agglomeration. Static can be adjustedto a satisfactory level by controlled use of reaction rate, quick changeof gas composition, selective use of static-neutralizing chemicals, andsurface passivation with aluminum alkyls.

In the case where the prepolymer is being used without the fluidizationaid, static can also be controlled by using small amounts of an inertconductive particulate material such as carbon black. The amount ofinert particulate material is that which is sufficient to controlstatic, but less than the minimum required for the material to act as afluidization aid, i.e., about 0.5 to about 0.9 percent by weight basedon the weight of the fluidized bed. Carbon black is the preferredantistatic material. The mean particle size of the inert conductiveparticulate material is in the range of about 0.01 to about 150 microns,preferably to about 10 microns. The mean particle size can refer to theparticle per se or to an aggregate as in the case of carbon black. Thecarbon black materials employed can have a primary particle size ofabout 10 to about 100 nanometers and an average size of aggregate(primary structure) of about 0.1 to about 10 microns. The surface areaof the carbon black can be about 30 to about 1500 square meters per gramand can display a dibutylphthalate (DBP) absorption of about 80 to about350 cubic centimeters per 100 grams. It is preferred to treat theparticulate material prior to its introduction into the reactor toremove traces of moisture and oxygen. This can be accomplished bypurging the material with nitrogen gas, and heating using conventionalprocedures.

The advantage of one embodiment of the above-described process lies inthe synergistic effects of having both prepolymer and fluidization aid.One synergistic effect relates to agglomeration protection. Thefluidization aid provides its least protection early in the growth ofthe polymer particle before an adequate protective coating has beenestablished. However, this is just when the prepolymer shell isthickest, and thus provides its maximum agglomeration protection.Conversely, the prepolymer provides least protection late in the growthof the polymer particle, when the shell may thin and allow sticky resinto come to the surface. However, this is just when the fluidization aidhas had maximum time to form its protective coating and is thereforemost effective. Another synergistic effect relates to catalystproductivity. High prepolymer residues are not desirable in the finalproduct because they impose a limitation on catalyst productivity.Higher productivities can therefore be achieved, while still maintainingagglomeration protection, by using small quantities of fluidization aid.Similarly, high fluidization aid residues are not desirable in the finalproduct because they negatively impact polymer properties. Lowerfluidization aid residues can be achieved while still maintainingagglomeration protection by using a prepolymerized catalyst. Thereforethe combination of fluidization aid with prepolymerized catalyst offersboth high productivity and low residues not achievable with either onealone.

The residence time of the mixture of comonomers, resin, catalyst, andliquid in the fluidized bed can be in the range of about 1.5 to about 8hours and is preferably in the range of about 2 to about 4 hours. Thefinal EPM or EPDM product can contain the following amounts of reactedcomonomers: about 35 to about 80 percent by weight ethylene; about 18 toabout 50 percent by weight propylene; and about 0 to about 15 percent byweight diene. The crystallinity, also in weight percent based on thetotal weight of the EPM or EPDM, can be in the range of zero(essentially amorphous)to about 10 percent by weight (nearly amorphous).The Mooney viscosity can be in the range of about 20 to about 150 and ispreferably about 30 to about 100. The Mooney viscosity is measured byintroducing the EPM or EPDM into a vessel with a large rotor, preheatingfor one minute at 100° C., and then stirring for four minutes at thesame temperature. The viscosity is measured at 100° C. in the usualmanner.

The fluidized bed reactor can be the one described in U.S. Pat. No.4,482,687 or another conventional reactor for the gas phase productionof, for example, polyethylene. The bed is usually made up of the samegranular resin that is to be produced in the reactor. Thus, during thecourse of the polymerization, the bed comprises formed polymerparticles, growing polymer particles, and catalyst particles fluidizedby polymerizable and modifying gaseous components introduced at a flowrate or velocity sufficient to cause the particles to separate and actas a fluid. The fluidizing gas is made up of the initial feed, make-upfeed, and cycle (recycle) gas, i.e., monomer and, if desired, modifiersand/or an inert carrier gas. A typical cycle gas is comprised ofethylene, nitrogen, hydrogen, and propylene, either alone or incombination. The process can be carried out in a batch or continuousmode, the latter being preferred. The essential parts of the firstreactor are the vessel, the bed, the gas distribution plate, inlet andoutlet piping, a compressor, a cycle gas cooler, and a product dischargesystem. In the vessel, above the bed, there is a velocity reductionzone, and in the bed, a reaction zone. Both are above the gasdistribution plate.

Variations in the reactor can be introduced if desired. One involves therelocation of the cycle gas compressor from upstream to downstream ofthe cooler and another involves the addition of a vent line from the topof the product discharge vessel (stirred product tank) back to the topof the reactor to improve the fill level of the product dischargevessel.

The advantages of the process in which the prepolymer is used withoutthe fluidization aid are: (i) the prepolymer provides protection againstagglomeration and allows operation of the fluidized bed above thesticking point of the polymer without the use of fluidization aid; and(ii) the EPR product has a better morphology than that produced by thestandard unprepolymerized catalyst precursor, i.e., the resin productparticles have a more spherical geometry and less surface asperities.

The advantages of the process in which the prepolymer is used togetherwith the fluidization aid are: (i) antiagglomeration protection isprovided at two crucial stages of the growth of the sticky EPRparticles, i.e., the prepolymer provides protection againstagglomeration in the early stages of the polymerization process and thefluidization aid provides protection in the later stages of the process;(ii) lower residues of the prepolymer and the fluidization aid areachieved because the two components complement each other in providingthe protection against agglomeration; and (iii) white fluidization aidspermit the production of colorable EPR products.

The patent application and patents mentioned in this application areincorporated by reference herein.

The invention is illustrated by the following examples:

EXAMPLES

In the examples, two reactors are used, alternatively, to carry out thepolymerization on different scales. They are referred to as Reactor Aand Reactor B.

Reactor A is a one liter, jacketed, stirred autoclave reactor andReactor B is a fluidized bed reactor, similar to the fluidized bedreactor described above, having an inner diameter of about 18 inches.

The catalyst system used in each of these reactors includes a vanadiumbased catalyst precursor, triisobutylaluminum (TIBA) as a cocatalyst,and chloroform (CHCl₃) as a promoter. The catalyst precursor is preparedusing conventional procedures such as the procedure described in U.S.Pat. No. 4,508,842, i.e., vanadium trichloride and an electron donor aresupported on dehydrated silica followed by a modification step to reducethe supported precursor with diethylaluminum chloride (DEAC). Thecatalyst system is then prepolymerized in a slurry prepolymerizer withethylene or ethylene and propylene to the desired level of prepolymer.It is believed that the ethylene homoprepolymer or theethylene/propylene coprepolymer forms a shell around the catalystprecursor.

Example 1

Prepolymerization

A catalyst precursor is prepared, as above, from vanadium trichloride(VCl₃), dehydrated silica, and diethylaluminum chloride (DEAC) with acomposition of 0.43 millimole of VCl₃ per gram of catalyst precursor, anexcess of tetrahydrofuran (THF), and 1.3 millimole of DEAC per gram ofcatalyst precursor. A 125 gallon prepolymerization vessel, as describedabove, is charged with 70 gallons of isopentane followed by 2 kilogramsof a 20 weight percent solution of triisobutylaluminum (TIBA)inisopentane. The mixture is heated to 50° C. for one hour to promote thereaction of the TIBA with any water present in the isopentane. Afterheating is complete, the batch is cooled to below 25° C., 240 grams ofchloroform are added as catalyst promoter, immediately followed by 1.5kilograms of catalyst precursor.

Prepolymerization is then started by pressuring the reactor to 30 psigwith ethylene. Polymerization begins within 5 minutes, as evidenced bythe steady feed of ethylene required to maintain the reactor pressureand by an increase in the reaction temperature to 30° C. The reactorpressure is gradually increased to 50 psig, and the reaction temperatureis gradually increased to 50° C. After sufficient ethylene has been fedto give a theoretical prepolymer loading of 100 grams of polymer pergram of supported catalyst, the feed is then stopped and the remainingmonomer in the reactor allowed to react. When the reactor pressurereaches a steady value and the batch has cooled to 30° C., the agitatoris shut off, the polymer allowed to settle, and the supernatant liquidremoved by a dip tube. Remaining isopentane is removed by heating thebatch to 40° C. at 0 psig with a nitrogen sparge. The dried prepolymeris screened through a 20 mesh screen kept inert by a nitrogen purge, and173 pounds of screened prepolymer are collected.

Polymerization

About 200 grams of sodium chloride are dried under vacuum at 115° C. forat least 12 hours. Reactor A is initially purged with nitrogen andheated to an internal temperature of 100° C. for at least 15 minutesunder a slow, continuous purge of nitrogen. The reactor is then cooledto 85° C. and the salt is taken from the vacuum oven while hot and addedto the reactor through a 0.5 inch port under a nitrogen flow. The saltbed is stirred at 300 rpm (revolutions per minute) and purged withnitrogen for an additional 15 minutes. The reactor jacket is then cooledto 50° C.

At a jacket temperature of 50° C., prepolymerized catalyst containingapproximately 0.03 millimole of vanadium is added to the reactor throughthe 0.50 inch port from a glass addition tube kept under nitrogen whilemaintaining a 150 rpm agitation of the bed. TIBA, as a 25 weight percentsolution in hexane, and CHCl₃, as a 1 molar solution in hexane, arecharged to a nitrogen purged 4 ounce bottle in a 50:1 Al/V mole ratioand a 1:1 Al/CHCl₃ mole ratio. This mixture is charged to the reactorand the 0.5 inch port is tightly capped. The reactor is purged brieflywith nitrogen through the vent line, sealed, and the stirring speedincreased to 300 rpm.

An initial quantity of 0.5 milliliters of ENB is fed to the reactor at arate of 0.5 milliliters per minute. At the same time, a mixture ofethylene, propylene, and hydrogen with a C3/C2 molar ratio of 1.5 and anH₂ /C2 ratio of 0.00 1 is fed to the reactor at an ethylene flow rate of2.5 liters per minute until the reactor pressure reaches 120 psig, atwhich point the flow rate drops to near zero momentarily. As thepolymerization reaction commences, the flow rate of the gas mixture, aswell as the reactor temperature, increases. At this point, the hydrogenfeed is turned off, the C3/C2 molar ratio is adjusted downward to avalue of 0.44, the ENB feed is adjusted to a rate of 0.05 milliliter perminute and the jacket temperature is adjusted to bring the internalreactor temperature to 65° C. The monomers are fed on demand for 105minutes, and the reaction is then terminated by stopping the flow ofmonomers and reducing the temperature of the reactor.

The reactor is vented, cooled, purged with nitrogen, and opened to takeout the mixture of salt and polymer product. The salt is washed out withwater to obtain about 60 grams of granular resin containing residualprepolymer. The residual amount of prepolymer in the resin and thecatalyst productivity are determined by mass balance, and the polymercomposition is determined by NMR (nuclear magnetic resonance) analysis.The properties are set forth in the Table. Granular EPDM is obtainedcontaining 13 percent by weight prepolymer.

Example 2

Example 1 is repeated except that the polymerization reactor is chargedwith 0.017 millimole of vanadium, and the polymerization is conductedfor 130 minutes. Granular EPDM is obtained containing 6 percent byweight prepolymer.

Example 3

Example 1 is repeated except that the prepolymerization is continued toa 55 gram/gram loading. The polymerization is conducted, using a chargeof 0.037 millimole of vanadium, for 40 minutes. Granular EPDM isobtained containing 11 percent by weight prepolymer.

Example 4

Example 3 is repeated except that the polymerization is conducted for100 minutes. The resin is agglomerated and granular EPDM is notobtained. The agglomerated resin contains 6 percent by weightprepolymer. This example shows that the prepolymer residue level thatprevents agglomeration for the catalyst of example 1 is not adequate forthe catalyst of example 3.

Example 5

Example 1 is repeated except that the polymerization is carried out inReactor B at a temperature of 60° C. and a C3/C2 molar ratio of 0.50. NoENB is fed to the reactor. Small amounts of carbon black are fed to thereactor to prevent static.

The process is operable and granular EPDM is obtained containing 31weight percent propylene; 3 weight percent residual prepolymer; and 0.7weight percent carbon black.

Example 6

Example 1 is repeated except that the prepolymerization is carried outwith a mixture of propylene and ethylene. The prepolymerized catalystcontains 2.7 weight percent propylene. Polymerization is performed inReactor B at a temperature of 60° C.; an H₂ /C2 molar ratio of 0.005;and C3/C2 molar ratio of 0.82. ENB is fed at a rate of 50 cubiccentimeters per hour and small amounts of carbon black are fed to thereactor to prevent static. The process is operable and granular EPDM isobtained containing 40 weight percent propylene; 0.5 weight percent ENB;12 weight percent residual prepolymer; and 0.8 weight percent carbonblack.

Example 7

Prepolymerization

A catalyst precursor is prepared, as above, from vanadium trichloride(VCl₃), dehydrated silica, and diethylaluminum chloride (DEAC) with acomposition of 0.43 millimole of VCl₃ per gram of catalyst precursor,excess tetrahydrofuran (THF), and 1.3 millimole of DEAC per gram ofcatalyst precursor. A 125 gallon prepolymerization vessel, as describedabove, is charged with 70 gallons of isopentane followed by 2 kilogramsof a 20 weight percent solution of triisobutylaluminum (TIBA) inisopentane. The mixture is heated to 50° C. for one hour to promote thereaction of the TIBA with any water present in the isopentane. Afterheating is complete, the batch is cooled to below 25° C., 240 grams ofchloroform are added as catalyst promoter, immediately followed by 1.5kilograms of catalyst precursor.

Prepolymerization is then started by pressuring the reactor to 30 psigwith ethylene. Polymerization begins within 15 minutes, as evidenced bythe steady feed of ethylene required to maintain the reactor pressureand by an increase in the reaction temperature to 30° C., and propylenefeed is then begun. The propylene feed rate is controlled with ametering valve to maintain a 0.02 propylene: ethylene weight ratio. Thereactor pressure is gradually increased to 50 psig, and the reactiontemperature is gradually increased to 50° C. over 6 hours. After 6hours, 77.3 kilograms of ethylene and 1.45 kilograms of propylene havebeen fed, to give a theoretical prepolymer loading of 50 grams ofpolymer per gram of supported catalyst. The feeds are then stopped andthe remaining monomers in the reactor allowed to react. When the reactorpressure reaches a steady value and the batch has cooled to 30° C., theagitator is shut off, the polymer allowed to settle, and the supernatantliquid removed by a dip tube. Remaining isopentane is removed by heatingthe batch to 40° C. at 0 psig with a nitrogen sparge. The driedprepolymer is screened through a 20 mesh screen kept inert by a nitrogenpurge, and 173 pounds of screened prepolymer are collected.

Polymerization

About 200 grams of sodium chloride are mixed with 1 gram of silicahaving an average aggregate size of 12 microns and a surface area of 140square meters per gram, and dried under vacuum at 115° C. for at least12 hours. Reactor A is initially purged with nitrogen and heated to aninternal temperature of 100° C. for at least 15 minutes under a slow,continuous purge of nitrogen. The reactor is then cooled to 85° C. andthe salt/silica mixture is taken from the vacuum oven while hot andadded to the reactor through a 0.5 inch port under a nitrogen flow. Thesalt bed is stirred at 300 rpm (revolutions per minute) and purged withnitrogen for an additional 15 minutes. The reactor jacket is then cooledto 50° C.

At a jacket temperature of 50° C., prepolymerized catalyst containingapproximately 0.03 millimole of vanadium is added to the reactor throughthe 0.50 inch port from a glass addition tube kept under nitrogen whilemaintaining a 150 rpm agitation of the bed. TIBA, as a 25 weight percentsolution in hexane, and CHCl₃, as a 1 molar solution in hexane, arecharged to a nitrogen purged 4 ounce bottle in a 50:1 Al/V mole ratioand a 1:1 Al/CHCl₃ mole ratio, along with an additional 0.4 millimole ofTIBA per gram of silica to further passivate the fluidization aid. Thismixture is charged to the reactor and the 0.5 inch port is tightlycapped. The reactor is purged briefly with nitrogen through the ventline, sealed, and the stirring speed increased to 300 rpm.

An initial quantity of 0.5 milliliters of ENB is fed to the reactor at arate of 0.5 milliliters per minute. At the same time, a mixture ofethylene, propylene, and hydrogen with a C3/C2 molar ratio of 1.5 and anH₂ /C2 ratio of 0.001 is fed to the reactor at an ethylene flow rate of2.5 liters per minute until the reactor pressure reaches 120 psig, atwhich point the flow rate drops to near zero momentarily. As thepolymerization reaction commences, the flow rate of the gas mixture, aswell as the reactor temperature, increases. At this point, the hydrogenfeed is turned off, the C3/C2 molar ratio is adjusted downward to avalue of 0.44, the ENB feed is adjusted to a rate of 0.05 milliliter perminute and the jacket temperature is adjusted to bring the internalreactor temperature to 65° C. The monomers are fed on demand for 90minutes, and the reaction is then terminated by stopping the flow ofmonomers and reducing the temperature of the reactor.

The reactor is vented, cooled, purged with nitrogen, and opened to takeout the mixture of salt, fluidization aid, and polymer product. The saltis washed out with water to obtain about 86 grams of granular resincontaining fluidization aid and prepolymer. The residual amounts offluidization aid and prepolymer in the resin, and the catalystproductivity, are determined by mass balance, and the polymercomposition is determined by NMR (nuclear magnetic resonance) analysis.The properties are set forth in the Table. Granular EPDM is obtainedcontaining 5 percent by weight prepolymer and 1.5 percent by weightfluidization aid.

Example 8

Example 7 is repeated except that no silica is mixed with the salt priorto charging to the reactor. After workup, 72 grams of resin containingprepolymer only is obtained with the properties set forth the Table.However, the resin is severely agglomerated and has to be scraped fromthe reactor surface. Granular EPDM is not obtained. The EPDM contains 6percent by weight prepolymer; but no fluidization aid. This shows thatlow levels of residual prepolymer are not in themselves capable ofproviding adequate agglomeration protection under these polymerizationconditions.

Example 9

Example 7 is repeated except that the catalyst precursor containsapproximately 0.92 millimole of vanadium per gram of catalyst precursor.The catalyst precursor is then prepolymerized to a prepolymerizedcatalyst precursor containing approximately 0.017 millimole of vanadiumper gram of prepolymer.

Polymerization is conducted for 45 minutes.

After workup, 34 grams of granular resin containing prepolymer andfluidization aid is obtained with the properties set forth in the Table.Granular EPDM is obtained containing 6 percent by weight prepolymer and3 percent by weight fluidization aid.

EXAMPLE 10

Example 9 is repeated except that the polymerization is continued for100 minutes and 2 grams of silica are mixed with the salt. After workup,71 grams of resin containing fluidization aid and prepolymer is obtainedwith the properties set forth in the Table. Granular EPDM is obtainedcontaining 3 percent by weight prepolymer and 3 percent by weightfluidization aid. This shows the synergism between prepolymer residueand residual fluidization aid. Lower prepolymer residues, and thushigher catalyst productivity, can be achieved by an increase in theresidual fluidization aid.

Example 11

Example 10 is repeated except that 1 gram of silica is mixed with thesalt. After workup, 65 grams of resin containing prepolymer andfluidization aid is obtained with the properties set forth in the Table.However, the resin is severely agglomerated and has to be scraped fromthe reactor surface. Granular EPDM is not obtained. The product contains3 percent by weight prepolymer and 1.5 percent by weight fluidizationaid. This shows that, at this lower prepolymer residue, higher amountsof fluidization aid are needed than are needed with a higher prepolymerresidue as in Example 1.

Example 12

Example 7 is repeated except that the prepolymerization is continueduntil 110 grams of olefin reacts per one gram of catalyst precursor. Theresulting prepolymerized catalyst precursor contains 3 percent by weightpropylene and 0.0039 millimole of vanadium per gram of prepolymer.

The prepolymerized catalyst precursor is added to the reactor; 6 gramsof silica are mixed with the salt; the polymerization is conducted for70 minutes; and the H₂ /C2 molar ratio is 0.012. After workup, 115 gramsof resin containing prepolymer and fluidization aid is obtained with theproperties set forth in the Table. Granular EPDM is obtained. Theproduct contains 5 percent by weight prepolymer and 5 percent by weightfluidization aid. This shows that adequate agglomeration protection canbe achieved when producing a lower molecular weight, stickier, resin byincreasing the residual level of fluidization aid.

Example 13

Example 12 is repeated except that 2 grams of silica are mixed withsalt. After workup, 90 grams of resin containing prepolymer andfluidization aid is obtained with the properties set forth in the Table.The resin is severely agglomerated and has to be scraped from thereactor surface. Granular EPDM is not obtained. The product contains 5percent by weight prepolymer and 2 percent by weight fluidization aid.This shows that residual levels of prepolymer and fluidization aid thatare adequate for high molecular weight products are not adequate forlower molecular weight, stickier, products.

                                      TABLE    __________________________________________________________________________            EXAMPLE            7    8      9    10   11     12   13    __________________________________________________________________________    Wt % C3 32   33     37   34   34     34   34    Wt % ENB            3    3      2    2    2      --   --    Melt Index            --   --     --   --   --     15   14    (g/10 min)    Cat. Prod.            1010 900    890  1900 1725   2800 2200    (g/g)    Prepolymer            5    6      6    3    3       4    5    residue (%)    Fluidization              1.5                 0      3    3      1.5   5    2    aid residue (%)    Morphology            granular                 agglomerated                        granular                             granular                                  agglomerated                                         granular                                              agglomerated    __________________________________________________________________________     Notes to TABLE:     1. Wt % C3 is the percent by weight of propylene based on the weight of     the EPDM product as determined by NMR analysis.     2. Wt % ENB is the percent by weight of ethylidene norbornene based on th     weight of the EPDM product as determined by NMR analysis.     3. Melt index (g/10 min) is determined under ASTM D1238, Condition E, at     190° C. and 2.16 kilograms. It is reported in grams per 10 minutes     4. Cat Prod (g/g) is the catalyst productivity based on the grams of EPDM     per gram of catalyst precursor.     5. Prepolymer residue (%) is the percent by weight prepolymer based on th     weight of the EPDM product.     6. Fluidization aid residue (%) is the percent by weight fluidization aid     based on the weight of the EPDM product.     7. Morphology is the structural form of the EPDM product, i.e., granular     or agglomerate.

Example 14

A prepolymerized catalyst is prepared as in Example 7 except that theprepolymerization is conducted without propylene and continued to abouta 100 gram per gram loading. Polymerization is then performed in ReactorB, a fluid bed reactor, at a temperature of 60° C.; an H₂ /C₂ molarratio of 0.0011; and a C3/C2 molar ratio of 0.80. Carbon black is fed tothe reactor as a fluidization aid. The process is operable and granularEPDM is obtained containing 30 weight percent C3; 2.6 weight percentENB; 11 weight percent residual prepolymer; and 5 weight percentfluidization aid.

Example 15

A prepolymerized catalyst is prepared as in Example 14 except that theprepolymerization is continued to about a 60 gram per gram loading.Polymerization is performed under the same conditions as in Example 8using carbon black as a fluidization aid. The process is operable andgranular EPDM is obtained containing 33 weight percent C3; 37 weightpercent ENB; 10 weight percent residual prepolymer; and 6 weight percentfluidization aid.

Example 16

This example involves the preparation of a prepolymer containing afluidization aid. A catalyst is prepared as in Example 7 except thatfollowing aluminum alkyl addition to the reactor, 800 grams of carbonblack, dried at 120° C. for 12 hours, are added as an isopentane slurry.The prepolymerization is then continued to a 50 gram per gram ofcatalyst loading. The screened prepolymer is a free flowing gray powder.

We claim:
 1. A process for the production of sticky EPM or EPDMcomprising contacting the monomers ethylene, propylene, and, optionally,one or more dienes, in a gas phase fluidized bed, at a temperature at orabove the sticking temperature of the product resin, underpolymerization conditions, with(i) a prepolymer containing a transitionmetal catalyst precursor with the proviso that the prepolymer is notsticky at the process temperature; (ii) an inert particulate materialhaving a mean particle size in the range of about 0.01 to about 150microns wherein the particulate material is either contained in theprepolymer or is independent of the prepolymer, (iii) a hydrocarbylaluminum and/or a hydrocarbyl aluminum halide cocatalyst, and,optionally, (iv) a halogen containing promoter; andwherein the combinedamount of prepolymer and inert particulate material is sufficient toessentially prevent agglomeration of the fluidized bed and the productresin.
 2. The process defined in claim 1 wherein the prepolymer ispresent in an amount of about 1 to about 12 percent by weight and theinert particulate material is present in an amount of about 1 to about15 percent by weight, both based on the weight of the product resin. 3.The process defined in claim 1 wherein the prepolymer is a homopolymerof ethylene or a copolymer of ethylene and propylene.
 4. The processdefined in claim 1 wherein the catalyst precursor is a vanadium compoundor the reaction product of a vanadium compound and an electron donor,said precursor being (i) unsupported or supported and (ii) unmodified ormodified with a modifier having the formula BX₃ or AlR.sub.(3-a) X_(a)wherein each R is independently an alkyl radical having 1 to 14 carbonatoms; each X is independently chlorine, bromine or iodine; and a is 0,1, or
 2. 5. The process defined in claim 1 wherein the monomers areethylene and propylene.
 6. The process defined in claim 1 wherein themonomers are ethylene, propylene, and a diene.
 7. The process defined inclaim 2 wherein the prepolymer is present in an amount of about 2 toabout 8 percent by weight and the inert particulate material is presentin an amount of about 1 to about 10 percent by weight.
 8. The processdefined in claim 1 wherein the particulate material is contained in theprepolymer.
 9. The process defined in claim 1 wherein the particulatematerial is independent of the prepolymer.
 10. A process for theproduction of a sticky EPDM comprising contacting the monomers ethylene,propylene, and a diene in a gas phase fluidized bed, at a temperature ator above the sticking temperature of the product EPDM, underpolymerization conditions, with(i) a prepolymer which is either ahomopolymer of ethylene or a copolymer of ethylene and propylene withthe proviso that (a) the prepolymer is not sticky at the processtemperature and (b) the amount of prepolymer used in the process islimited to that amount which will provide about 2 to about 8 percent byweight of prepolymer in the product EPDM based on the weight of theproduct EPDM, said prepolymer containing a vanadium based catalystprecursor, which, optionally, contains an electron donor, a support,and/or a modifier having the formula BX₃ or AlR.sub.(3-a) X_(a) whereineach R is independently an alkyl radical having 1 to 14 carbon atoms;each X is independently chlorine, bromine, or iodine: and a is 0, 1, or2; (ii) silica or carbon black having a mean particle size in the rangeof about 0.01 to about 10 microns in an amount of about 1 to about 10percent by weight based on the weight of the product EPDM wherein thesilica or carbon black are either contained in the prepolymer or areindependent of the prepolymer; and (iii) a hydrocarbyl aluminum and/or ahydrocarbyl aluminum halide cocatalyst; and (iv) a halogen containingpromoter,wherein the combined amount of prepolymer and inert particulatematerial is sufficient to essentially prevent agglomeration of thefluidized bed and the product resin.